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• 98-03-3 thiophene-2-carbaldehyde 
• 95-54-5 1,2-diamino-benzene 
• 88-74-4 2-nitro-aniline 

Relevant academic research and scientific papers

A simple and efficient mechanochemical route for the synthesis of 2-aryl benzothiazoles and substituted benzimidazoles

An efficient and versatile mechanochemical route to 2-aryl benzothiazoles and both 2-substituted and 1,2-disubstituted benzimidazole derivatives has been developed via a simple mortar-pestle grinding method. The mechanochemical agitation was found to be sufficient for smooth condensation between a variety of aromatic aldehydes and o-aminothiophenol/o-phenylenediamine followed by cyclization leading to the formation of the corresponding 1,3-benzazoles. The salient features of this new protocol are catalyst-free reaction, cleaner reaction profiles, absence of a work-up step, high yields, and short reaction times.

Water extract of onion catalyst: An economical green route for the synthesis of 2-substituted and 1,2-disubstituted benzimidazole derivatives with high selectivity

An efficient, environmental friendly and substrate controlled method of synthesis of 2-substituted benzimidazole derivatives 3 and 1,2-disubstituted benzimidazole derivatives 4 with high selectivity has been achieved from the reaction of o-phenylenediamine 1 and aldehydes 2 in the presence of water extract of onion and selecting suitable reaction medium. This method is widely applicable for variety of aldehydes such as aromatic/aliphatic/heterocyclic aldehydes and 1,2-diamines to afford 2-substituted benzimidazole derivatives 3 and 1,2-disubstituted benzimidazole derivatives 4 in good to excellent yields (up to 96%). The developed method of water extract of onion catalysis produced 2-substituted benzimidazoles 3 from aromatic aldehydes having electron-withdrawing groups, whereas aromatic aldehydes bearing electron donating groups selectively furnished 1,2-disubstituted benzimidazole 4 derivatives. The process described here has several advantages of cheap, low energy consumption, commercially available starting materials, operational simplicity and nontoxic catalyst. The use of water extract of onion makes this present methodology green and giving a useful contribution to the existing methods available for the preparation of benzimidazole derivatives. In addition, Hammett correlation of substituent constant (σ) vs percentage (%) yield has been established.

Eco-friendly synthesis of condensed nitrogen heterocycles: A brief experience from our group

In order to develop eco-friendly syntheses of condensed nitrogen heterocycles, solvent-free syntheses on solid acidic catalysts and aqueous reactions using a phase transfer catalyst (PTC) were successfully carried out. The catalysts used were (i) TLC-grade silica gel G (SiO2), (ii) SiO2 doped with 10 mol% phosphoric acid (H3PO 4-SiO2), (iii) Montmorillonite K10 clay (K10), (iv) acid-washed K10 clay (acid-clay), (v) K10 doped with one equivalent (with respect to substrate) of tosic acid (TsOH-K10) and (vi) cetylpyridinium bromide (CPB) (5 mol%) as the PTC. The reactions were carried out at room temperature (rt), at 60-70°C (oven) or under microwave irradiation (MWI).

The synthesis of benzimidazole derivatives in the absence of solvent and catalyst

Differently substituted benzimidazoles have been synthesised from o-phenylenediamine and arylaldehydes or arylmethylene-malononitriles absorbed on silica gel. The reaction was carried out by intermittent grinding or by a microwave-assisted technique under solvent- and catalyst-free conditions giving good yields of the products.

Tosic acid-on-silica gel: A cheap and eco-friendly catalyst for a convenient one-pot synthesis of substituted benzimidazoles

2-Substituted and 1,2-disubstited benzimidazoles were prepared efficiently from o-phenylenediamines and aryl aldehydes using p-toluenesulphonic acid (5∈mol%)-on-silica gel as a cheap and environmentally benign catalyst.

Application of sulfamic acid as an eco-friendly catalyst in an expedient synthesis of benzimidazoles

Sulfamic acid, an eco-friendly and zwitterionic solid, proved to be a very efficient catalyst for the reaction of ortho-phenylenediamine with aryl aldehydes in ethanol at room temperature to furnish both 1-arylmethyl-2-aryl- and 2-arylbenzimidazoles in very good to excellent overall yields.

Indium-mediated reductive intermolecular coupling reaction of 2-nitroaniline with aromatic aldehydes to benzimidazoles

2-Nitroaniline and aromatic aldehydes were coupled to give benzimidazoles in high yields in the presence of 2-bromo-2-nitropropane and indium at room temperature.

A New Type of Reaction between o-Phenylenediamines and Aromatic Aldehydes to Give 2,3-Diarylquinoxalines

A new type of reaction between o-phenylenediamines and aryl aldehydes at high temperature is reported. The synthesis of 2,3-diarylquinoxalines by this procedure is described.